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Amedee, Toyota Technician
Category: Toyota
Satisfied Customers: 24088
Experience:  ASE certified tech advanced level specialist. Wisconsin certified emissions state inspector
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2000 Toyota Sienna: cold weather..cylinders..fuel sensor

Resolved Question:

2000 Toyota Sienna, Very hard to start in cold weather, takes countless revolutions but will finally start. Had codes for random misfire on multiple cylinders, did a complete tune up, fuel filter, wires, boots, and a new cam sensor, checked fuel pressure, was at 50 psi, Still have same problem, one thing I did notice is that the spark seemed very weak except when it was trying to start the spark would get stronger, no codes are present now, but still has the same problem.
Submitted: 5 years ago.
Category: Toyota
Expert:  Amedee replied 5 years ago.
Hello and Welcome to Just Answer. My name is XXXXX XXXXX I will try my best to assist you and your 100% satisfaction is my goal. I have been working on these vehicles for over 10 years so I am very familiar with this system and how it works. However, keep in mind, that I need some solid concrete facts/evidence from you in order to give you a good answer about your vehicle. Please realize that all my answers are based solely on the info that you provide me with....

Have you checked the fuel pressure?

Are there any codes in the computer?
Customer: replied 5 years ago.

fuel pressure is 50 psi

there are no codes

i did notice that the spark looks weak until it trys to start then it get real brite

Expert:  Amedee replied 5 years ago.
It sounds to me like you have a bad IAC motor or a bad cam or crank sensor causing your hard start issue. You can try holding the throttle open a little bit when cold and see if the engine starts right away and runs ok as long as holding down a little on the throttle. If so, check and clean the Idle Air Control (IAC) valve. Check engine temperature on the scan tool to verify the Engine Control Module (ECM) knows the engine is cold.

Potential Causes:
Engine Coolant Temperature (ECT) Sensor
Idle Air Control (IAC) Valve
cam/crank sensor
Customer: replied 5 years ago.
changed the cam positioning sensor and it did not help, i have cleaned the IAC did not help. If you hold the throttle to the floor or just a little bit it takes countless revolutions before it finally starts. After it starts it will miss occasionally but will start right away after warmed up. I have hooked up my scanner and the ECM tells me the coolant temp. One other thing I did notice when holding throttle wide open and the motor is trying to start I will get a popping noise through the air filter but once it starts the noise goes away and the vehicle will run fine.
Expert:  Amedee replied 5 years ago.
Well, maybe you just have a bad crank sensor.. the signal back to the pcm might just be bad. It might be good enough for the computer to pick up on but the signal may be erratic. You will need to check this with a lab scope.

Also, just be sure that the fuel pressure does not leak down.
Customer: replied 5 years ago.
My scanner has a labscope built into it, and does not show any erratic or missing gaps, for the rpm signal.
Expert:  Amedee replied 5 years ago.

Then it sounds like the IAC is going to be at fault.
Customer: replied 5 years ago.
Once it does start, the high idle does come in, wouldn't that be the IAC working the way it's supposed to?
Expert:  Amedee replied 5 years ago.
I just did a search for your specific vehicle for "hard start". just about every one of them came back as a bad IAC motor.
Customer: replied 5 years ago.
I have tried all that you recommended already and none of them have worked. You don't have any other ideas? When we added fuel injection cleaner to it it would start easier in the morning but even that isn't working anymore. And the fuel pressure is good.
Expert:  Amedee replied 5 years ago.
You could just have a bad PCM.

Try adding fuel to the intake to see if this helps.

However, if I were you, I would replace the IAC motor before going any further.
Customer: replied 5 years ago.
Thank you. Ill try the IAC motor, but when I add fuel it makes it worse.
Expert:  Amedee replied 5 years ago.
Yeah.. it sounds just like a bad IAC motor to me... I would start there.

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